Actively Controlled Hood for Machinery Noise

本研究的第一阶段研究了机械外壳的设计特点，作为主动消除噪声控制的应用。减少通过建筑物传播的噪音是一种广泛存在于各种情况下的需求。在这种方法中，低频降噪是通过主动控制概念实现的，高频降噪是通过被动控制实现的。控制的性能估计表明，需要多个执行器在整个空间角度频谱的主动控制频率范围内消除外壳传输的噪声。在该研究项目的第二阶段，重点是开发三维外壳的分析和数值模型，并评估结构参数在实现低频噪声滤波器目标中的作用；评估地面观察员的选择；开发具有成本效益的方法来驱动表面面板；评估备选传感器和将其嵌入表面面板模块的设计概念；开发原型外壳的具体设计，包括主要结构和带有传感器和执行器的表面模块；并利用样机外壳对上述概念进行了实验评估

Phase I of this study had examined the design characteristics of machinery enclosures as an application for noise control by active cancellation. Reduction of noise transmitted through structures is a need that pervades a wide variety of situations. In this approach, noise reduction at low frequency is achieved via active control concepts, and at high frequency--using passive control. Performance estimates for control demonstrate the need for multiple actuators to cancel enclosure transmitted noise throughout the active control frequency range over the full spectrum of spatial angles. In Phase II of this research project, the emphasis is on developing analytical and numerical models of three-dimensional enclosures and assessing the role of structural-parameters in achieving the objectives of a low- frequency noise filter; evaluating surface observer options; developing cost-effective approaches for actuating the surface panels; evaluating alternative sensors and design concepts for embedding them into a surface panel module; developing a specific design for a prototype enclosure including primary structure and surface modules with sensors and actuators; and experimentally evaluating the above concepts using the prototype enclosure.***//